Porous structures of concrete, masonry, stone and wood, including buildings, roads, bridges, tunnels, monuments, sculptures and other outdoor art works are exposed to the deleterious effects of multiple environmental hazards. Attack by acid rain, salts, extreme temperatures and various atmospheric pollutants causes gradual but persistent deterieration in these structures. The presence of commonly used reinforcing steel members embedded in most of these porous structures increases the damage and deterioration created by corrosion and oxidation of the steel following erosion of the surrounding masonry, all caused by the airborne pollutants in today's atmosphere. These pollutants, acid in character, easily penetrate and react with the lime salts present in all masonry, the result being slow and constant erosion, cracking, crumbling and eventual collapse of the exposed porous structures.
Presently used methods of preservation have provided short-term protection, at best. Waterproofing materials, protective compounds and paints, when applied to structures by standard brush, spray or roll-on methods, achieve only shallow penetration by capillary action; a single coat is insufficient, and a second coat tends to clog the porous structure's breathing passages, as reported in National Bureau of Standards Technical Report No. 1118. With the surfaces of the porous structures clogged and sealed in this manner, internal stresses and pressure develop within the structures, created by the effect of thermal changes on the ever-present moisture in masonry; as a result, the trapped vapor pressure generated thereby breaks through, cracks, delaminates and destroys the protective coating.
Numerous other methods have been used in attempts to preserve porous structures of concrete or masonry. One method is to break open the structure, clean the rusted reinforcing steel, repaint or replace the steel where necessary, then repair the outer masonry or concrete structure. Another method is to drill holes in the structures where reinforcing steel members exist, apply a preservative material with a gun applicator under manual or pump pressure, then refill and repair the masonry. Still another method used on roadbeds involves cutting elongated slots or grooves, filling the slots or grooves by gravity with liquid preservative material, which may or may not reach the reinforcing steel, thereafter filling the slots or grooves with roadbed coating material. Electrical anodic treatment has also been used, also requiring the breaking open and repairing the concrete. The above preservation methods are slow and costly processes, and on roads are also inconvenient to travelers during such repairs.
In the case of wood preservation, the current application of paint, shellac, epoxy or urethane resins to wood surfaces results in protection which lasts from a few seasons to a year or so before the need arises for scraping and sanding the treated surface and repeating the coating application; damage to the original coating results from the shallow penetration and sealing effect of applications made by brush, roll-on or spray. The cellular resin structure of wood tends to cause a chemical migration in the wood when thermal expansion stresses, such as hot and cold weather spells, are imposed. In the summer, the expansion stresses cause these coatings to expand as a result of forces emanating from the wood's cellular resins; in the winter, the contraction stresses cause these coatings to crack and peel, allowing moisture, acid rain and pollutant intrusion to cause "lift-off" of the coatings when freeze-thaw cycles occur. Thereafter, moisture- and pollutant-absorption into the wood fibers accelerates wood decay.
The prior art discloses some presently used methods and apparatus for preservation of porous masonry walls; among them are U.S. Pat. No. 4,204,495 to Wyner disclosing the design of a high-speed pulsating air device, and U.S. Pat. No. 4,395,457, also to Wyner, dealing with the thermal insulating effect achieved by entrapment of the air cells existing between masonry particles, thereby creating a multi-barrier thermal insulating system that prevents heat or cold from escaping through the walls of a masonry structure, thus reducing high energy consumption and fuel costs. Also, U.S. Pat. No. 4,153,743 to Caramanian and U.S. Pat. No. 4,342,796 to Brown disclose surface treatments of concrete with sealant materials, but without injecting the sealant into the porous structure.